Many conventional motor vehicles, such as the modern day pickup truck, are equipped with a pivotable end gate that closes off the end of a rear storage area. The traditional end gate (more commonly known as a “tailgate”) is a door assembly extending transversely across the width of a rear portion of the vehicle. The end gate is normally hinged to the vehicle body at opposing side edges, near the bottom of the door assembly. The end gate is often mounted to two rear pillars between body side-panels that cooperatively form a vehicle storage area, such as the bed or box of a pickup truck or the rear cargo compartment of a sport utility vehicle (SUV). The end gate is operable to be unlatched, and swung from a vertical, closed position to a horizontal, open position that is approximately coplanar with an interior floor surface of the vehicle storage area.
Removal of the end gate may be desired to provide access to the bed without interference from the end gate, to attach loading ramps directly to the floor of the bed, or for other purposes for which flexibility of the bed and access to the bed is beneficial. On some vehicles, one or more cables are employed to provide additional support for the end gate when it is in the open position. The cables may have spring clips at one end that clip to a hook on a vehicle sidewall. Thus, the cables are unclipped from the hooks to release the cables from the sidewall, prior to lifting the end gate to remove the end gate from the vehicle.
Some end gate assemblies include a counterbalancing hinge assembly for assisting movement of the tailgate during opening and closing thereof. Different hinges can be used to produce various desired hinging characteristics. Torque (or torsion) rods have been used within prior art hinge devices to aid in hinging the end gate to the vehicle body. Deflection of the torque rod is used to counterbalance the weight of the end gate to aid in the opening and closing thereof. Specifically, the torque rod reduces the effort required to raise and lower the tailgate by storing energy in the twisting of the torque rod during opening/lowering from the residual kinetic energy generated by the tailgate. Although torque rod based tailgate counterbalancing hinge designs, such as those discussed above, reduce efforts in opening and closing the tailgate, the end gate can cause an objectionable impact and noise if allowed to free fall into the open position.
Some modern pickups and SUVs are also equipped with a damper on either side of the end gate to provide damped lowering of the end gate upon opening. In conventional end gate dampers, a pneumatic cylinder-and-piston assembly is coupled at one end to an upper portion of the end gate, and the other end to the vehicle body. When the tailgate is unlatched, the piston, under the weight of the end gate, compresses entrained air inside of the cylinder. The air is evacuated through a reduced-size orifice in the cylinder, creating a linear counterforce which acts to dissipate kinetic energy and thereby slow movement of the end gate.